Nord Quantique Reports Sharp Drop in Quantum Prep and Readout Errors

Nord Quantique says it has cut one of the more stubborn error sources in its quantum computers to below 0.1%. In a paper posted to arXiv, the Canadian company reports state preparation and measurement errors, known as SPAM errors, around 100 times lower than earlier results in comparable systems. The work has not yet been peer-reviewed.

What SPAM errors are

Every quantum computation starts by setting a qubit into a known state and ends by reading it back out. Mistakes at either end, a badly prepared starting state or a misread result, are SPAM errors, and they cap how well the rest of the machine can perform. No error-correction scheme can fully recover from a computation that began with the wrong input or ended with a wrong measurement.

That weakness has been a particular problem for GKP systems, the bosonic approach Nord Quantique uses, where its SPAM numbers had trailed other benchmarks. The company says its new figure is in the range routinely visible on leading superconducting transmon platforms, which would close a longstanding gap for its architecture.

How they did it

The method is a repeat-until-success protocol. Rather than correcting a state in real time, which needs fast and complex classical control, the system prepares a state, checks whether the preparation worked, and either keeps it or discards it and tries again. Nord Quantique says this is simpler to run and reuses the same error correction already built into its machines, with no hit to logical error rates.

The company also applied the approach to preparing magic states, the specialized states needed for the operations that make a quantum computer universal. High-quality magic-state preparation is one of the more resource-heavy problems across the field, so doing it within the same architecture is the more notable claim in the paper.

CEO Julien Camirand Lemyre tied the result to the company’s stated goal of reaching fault-tolerant quantum computing by 2030.